Why does eAG differ from my fingerstick average?

A1c reflects the prior 8-12 weeks weighted to the most recent 4 weeks. Fingersticks miss overnight + post-meal peaks. Use CGM (continuous glucose monitor) for closer agreement.

A1c units (NGSP vs IFCC)?

US/UK use NGSP (%). IFCC uses mmol/mol. Conversion: NGSP% = (IFCC mmol/mol × 0.0915) + 2.15. This calc uses NGSP %.

Inaccurate in iron deficiency anemia, hemoglobinopathies (SS, SC, β-thal), recent transfusion, kidney failure on EPO. Use fructosamine or glycated albumin in those cases.

Generally <7% for most adults; <6.5% if achievable safely; <8% in elderly with comorbidities. Individualize. Source: ADA Standards of Care 2026.

Is this medical advice?

No. Educational tool only. Clinical decisions require labs, history, and a clinician.

A1c to eAG (Estimated Average Glucose) Calculator

Convert HbA1c (%) to estimated average glucose: eAG (mg/dL) = 28.7 × A1c − 46.7. ADAG / Nathan 2008.

Result

Estimated Average Glucose (eAG)

154.2 mg/dL

A1c 7% → 154.2 mg/dL = 8.54 mmol/L. Diabetes range (≥6.5%).

A1c (%)7
eAG (mg/dL)154.2
eAG (mmol/L)8.54
ADA categoryDiabetes range (≥6.5%)

Diabetes range (≥6.5%)

4 % A1c7 % A1c12 % A1c

ADA diagnostic thresholds: 5.7% (pre-DM), 6.5% (DM).

Source: Nathan DM et al., "Translating the A1C Assay Into Estimated Average Glucose Values," Diabetes Care 2008;31(8):1473–78 (ADAG study).

Not medical advice — A1c is inaccurate with iron-deficiency anemia, hemoglobinopathies (SS/SC/β-thal), recent transfusion, or EPO use; consider fructosamine or glycated albumin in those cases. Educational tool — not a diagnosis or treatment plan.

Step-by-step

eAG (mg/dL) = 28.7 × A1c − 46.7 = 28.7 × 7 − 46.7 = 154.2.
eAG (mmol/L) = 1.59 × A1c − 2.59 = 8.54.
(Conversion: mmol/L × 18.018 = mg/dL.)

How to use this calculator

Enter HbA1c (%).
Choose output units (mg/dL US default, mmol/L international).
Compare eAG to your fingerstick log average — should be within 30 mg/dL.

About this calculator

eAG (estimated average glucose) translates HbA1c into the same units as a fingerstick reading. Linear regression from the ADAG (A1C-Derived Average Glucose) Study (Nathan et al., Diabetes Care 2008;31:1473) across 507 subjects with T1DM, T2DM, or no diabetes. Formula: eAG (mg/dL) = 28.7 × A1c − 46.7. ADA categories: <5.7% non-diabetic, 5.7-6.4% pre-diabetes, ≥6.5% diabetes. Source: American Diabetes Association Standards of Care 2026 (annual update); Nathan DM et al. "Translating the A1C Assay Into Estimated Average Glucose Values" Diabetes Care 2008. **Not medical advice — use clinical context and labs, not a single number.**

Frequently asked

Nathan DM et al., Diabetes Care 2008;31(8):1473-78. The ADAG Study correlated A1c with continuous glucose monitoring across 507 subjects of mixed diabetes types.